The invention relates generally to a wood-type golf club head and, more particularly, to a golf club head having a lightweight crown.
A wood-type golf club head includes a load-bearing outer shell with an integral or attached strike plate. Today's club head is typically formed of metal material and has a hollow cavity. The metal body may comprise several portions welded together or may include a cast body with a separate sole plate or strike plate that is welded in the appropriate location.
Most club heads today are made of a strong, yet lightweight metal material such as, for example, a titanium, steel or aluminum alloy. There have also been heads fanned of carbon fiber composite material. The use of these materials is advantageous for the larger club heads now sought by golfers, i.e., at least 300 cc and up to about 500 cc in volume. The larger sized, yet conventionally weighted, club heads strive to provide larger “sweet spots” on the striking face and club moments of inertia that, for some golfers, make it easier to get a golf ball up in the air and with greater accuracy.
Various attempts have been made to attain an improved coefficient-of-restitution (“COR”) for golf club heads, with much attention paid to the design of face plates having variable thickness. However, the durability of very thin portions of the face plate continues to be a problem. Such face plate designs are limited by the high impact loads to which these club heads are subject, in particular at the junctions of the face plate with the crown and sole of the club head.
Titanium alloys are particularly favored in club head designs for their combination of strength and light weight. However, the material can be quite costly. Steel alloys are more economical; however, since the density of steel alloys is greater than for titanium alloys, steel club heads are limited in size in order to remain within conventional head weights while maintaining durability.
Composite club heads, such as a carbon fiber reinforced epoxy or carbon fiber reinforced polymer, for example, are an alternative to metal club heads. A notable advantage is the relatively light weight compared to stainless steel alloys. However, these club heads have suffered from durability and performance qualities associated with composite materials. These include higher labor costs in manufacture, undesirable acoustic properties of the composite material, shearing and separation of the layers of composite plies used to form the striking surface of the club head and relatively low COR for composite faces.
The areas of the club head that are subject to the greatest wear, the face and sole, have been reinforced in some instances by providing a metal plate in one or both regions. Integrated face and hosel constructions have also been done. However, durability at the junctions of the composite and metal materials continues to be a problem. Further, when the majority of the body of the club head is of composite material, there may still remain the problem of adequately fixing one or more weighting elements within the head body. The mere increase in volume of the club head may not provide the proper location of the center of gravity of the club head for greater forgiveness in off-center hits.
With regard to hybrid metal-composite club heads, U.S. Pat. Nos. 5,328,176, 5,410,798, and 5,624,331 to Kun-Nan Lo disclose composite-metal golf club heads having a metal casing with an inner member or core of composite material. The inner member reinforces the thin walls of the metal casing in U.S. Pat. Nos. 5,410,798, 5,624,331. The crown comprises one or two carbon fiber composite portions. The single composite crown portion of U.S. Pat. No. 5,410,798 is attached to the upper ends of the composite member during the heating portion of the manufacturing process. The double composite crown portions of U.S. Pat. No. 5,624,331 are separated by a reinforcing central rib of the metal casing. U.S. Pat. No. 5,328,176 discloses a metal reinforcing plate that is fixed to the front face and wraps around the composite head from front to back.
Published U.S. Patent Application No. 2002/0049310 to Cheng et al. discloses a metal golf club head having a carbon-fiber cover that incorporates the entirety of the upper wail and a majority of the side walls at the toe, rear and heel ends of the head body. The position of the center of gravity of the head is accomplished by the size and placement of weight plugs in the sole and rear side wall. The attachment of the carbon-fiber cover is accomplished by insertion of a bladder through the hole for the plug in the sole and application of aluminum oxide sand where the carbon-fiber cover contacts the metal base and face of the head. The bladder is inflated, and the aluminum-oxide sand adhesively attaches the cover to the rest of the club head during a heating process.
Published Japanese Application No. 05-317465 discloses a golf club head having a hole cut into the crown part. The hole may be closed with a plate of a transparent and lightweight resin. This device allows the weight of the replaced metal material to be substantially distributed to the sale, lowering the center of gravity. An initial speed of a ball is increased and an amount of spin can be decreased, whereby distance can be increased.
Metal, composite and hybrid metal-composite club heads have long suffered from poor acoustic properties. That is, golfers are accustomed to—and desire—a particular range in pitch tone generated by the golf ball impacting the striking face. Some prior club heads have used a foam filling in order to alter the sound while attempting to minimize any adverse impact on performance. While metal club heads have become better matched to golfers' acoustic preferences, composite club heads generally lack acoustic appeal.
It should, therefore, be appreciated, there is a need for a golf club head having a high COR and improved durability and acoustic qualities, which is cost effective and simple to manufacture. The present invention fulfills this need and others.